This article contains spoilers for Halo episode 1.
Halo episode 1 saw the Master Chief discover a mysterious artifact on the planet Madrigal. By the time of Paramount+'s Halo series, the Human-Covenant War has been raging for years. Already the UNSC has learned Spartans are their only real defense against the alien threat of the Covenant, but a mission to the Outer Colony world of Madrigal takes an unexpected twist when the Master Chief learns an Elite is attempting to retrieve something.
The object may only be small, but it's clearly powerful; when the Master Chief touches it there's a flare of energy, and he experiences visions of memories - possibly his own, possibly the memories of whoever created this ancient device. Later in the episode, the Master Chief touches it again, and this time it generates what seems to be an electromagnetic pulse of some kind that helps him escape the UNSC forces on the planet Reach. Dr. Halsey is fascinated, presumably intuiting that this is the real reason the Covenant's Prophets ordered the invasion of Madrigal in the first place.
Viewers can deduce a lot more about the artifact than Dr. Halsey, however. In the Halo franchise, the galaxy was once ruled by an ancient race who are known as the Forerunners. The galaxy is littered with Forerunner relics, and the greatest of these are the Halo Rings - weapons designed to extinguish all life in a section of the cosmos, the ultimate defense against the parasitic infection known as the Flood. The Covenant revere the Forerunners, believing they did not die but rather ascended to a higher plane of existence, and they seek to rediscover the Halo Rings and activate them. The artifact seen in Halo episode 1 is clearly of Forerunner origin, and interestingly, its layout is reminiscent of mapmakers seen in some of the Halo games. That suggests the holographic images the Master Chief sees when he touches the artifact serve some sort of navigational purpose - perhaps even pointing to the location of a Halo Ring.
But this Forerunner artifact seems to be far more than a mere map. It clearly contains a significant power source, suggesting it is supposed to be taken to a specific location and used to activate it. Given that's the case, the Master Chief may well have stumbled upon both a map to lead him to a Halo Ring and a power source (perhaps an Index) to awaken it from its current dormant phase. If this is indeed the case, the stakes of the Human-Covenant War have suddenly become higher than ever before - and the Master Chief doesn't even know it.
The Covenant know humans are required to activate Forerunner technology, and they have their own agent to help them do so. No doubt they'll aim to get this mysterious Forerunner artifact back, especially if it really is essential to activate a Halo Ring. The disturbing question is whether its use generates a signal the Covenant can detect; in the original Halo timeline the Covenant possess devices called Luminaries that can register flares of Forerunner energy. It's quite possible the Master Chief has accidentally given away Reach's location - which would mean the Covenant attacked in force to get it back.